1. Field of the Invention
The invention relates generally to a method for supplying a plurality of system components of an electro-technical system with a common reference signal. In addition, the invention relates to a corresponding reference signaling arrangement for supplying a plurality of system components of an electro-technical system with a common reference signal. In addition, the invention relates to a reference signaling facility, an electro-technical system comprising a number of system components and a system component for the system.
2. Description of the Related Art
At present many electro-technical systems, for example electro-technical devices or subassemblies or subassembly arrangements, are of a modular design. This is true especially of medical engineering systems such as magnetic resonance systems or computer tomography systems.
To synchronize the functions of the individual components of such medical engineering systems, the appropriate control signals must be sent to the components. Thus, for example European Patent Document EP 0 350 120 A1 describes how different magnetic field generators and the transmitters/receivers of a magnetic resonance system are controlled for transmission and receipt of the radio frequency signals from a common open-loop and closed loop control unit. This control is usually undertaken over a data bus. To this end, German Patent Document DE 197 22 221 A1 proposes implementing part of the bus as an optical bus, in which the control signals are transmitted over an optical fiber in order to avoid the interference within the radio frequency range caused by electrical control signals. For the same reasons, U.S. Pat. No. 5,869,966 proposes transmitting a switching signal for activating and deactivating a radio-frequency antenna in a magnetic resonance system by means of an optical fiber link from a control device to the radio-frequency antenna. For this reason too it is proposed in German Patent Document DE 42 00 992 A1 that the received magnetic resonance signals first be prepared and convened into optical signals and then transmitted optically to the controller located outside the radio frequency area. In this case the control signals needed and the energy needed in the radio frequency range for signal preparation are made available using non-electrical methods, e.g. via optical signals or thermal energy transmission methods. Furthermore, a method is specified in German Patent Document DE 101 48 442 C2 for preparing the magnetic resonance signals in a suitable manner for such transmission over optical fibers.
Furthermore a common reference signal, for example a clock signal, is often needed for precise timing of the synchronization of the individual system components or modules. A typical example is a modern magnetic resonance system, in which it is possible to activate different antenna elements or modes separately, to emit radio frequency pulses over the relevant antenna elements or in the relevant modes, or to receive magnetic resonance signals via the relevant antenna element or in the mode. For this to be done a separate transceiver element is needed for each antenna element or each mode. These transceiver components must operate synchronized with each other.
To supply the different components of an electro-technical system with reference signals a suitable electronic reference signal has previously usually been generated by a reference signal generator and distributed over electrical paths to the wide diversity of components. FIG. 1 shows a typical layout of such a conventional reference signaling arrangement. As a rule, the reference signal is generated with a VCO (Voltage Controlled Oscillator) and transferred to an amplifier which passes the electrical reference signal to a so-called “splitter” in which the reference signal is split up over the desired N transmission channels, with N being the number of the system components to be supplied. The reference signals are generally transferred from the splitter to the individual components over coaxial cables. Each of the system components has a defined input impedance which operates as an electrical load at the end of the respective coaxial cable.
This distribution method has various disadvantages. On the one hand, a significant output power of the reference signal generator is necessary for a larger number of system components to be supplied. Furthermore each load, i.e. each system component, connected at the end of a coaxial line, has a specific coefficient of reflection. This reduces the electrical isolation between the outputs of the splitter and thereby increases the risk of crosstalk between the individual system components. The multiple reflections can also cause a significant deterioration in the signal quality of the reference signal to be distributed. In addition, the distance between the output of the splitter and the input of the individual system components should not be too great, since otherwise the maximum permissible frequency of the reference signal is very restricted. The concepts currently employed are thus only sufficiently good if the number of system components to be supplied is small and the components are preferably arranged in a housing or especially preferably on a circuit board. In addition, the frequency of the reference signal is almost always greatly restricted. This means that as a rule reference signals with a frequency of over 100 MHz cannot currently be transmitted.